The longer you own an electric vehicle, the lower its global warming emissions are likely to become. Why? As some of the oldest, dirtiest coal plants are being retired and investments in renewable electricity increase, the global warming emissions that result from generating a given amount of electricity are estimated to fall nationwide by an average of about 13 percent by 2025.

That means, for 70 percent of Americans, charging their electric vehicle (EV) on the regional electricity grid in 2025 would result in lower global warming emissions than even today’s most efficient gasoline hybrid, the 50 mpg Prius. While that’s good news, it could be even better. By investing in more renewables and retiring more coal plants over the next decade, using electricity as a transportation fuel would deliver even greater global warming benefits than projected.

How will changes in the grid affect the emissions from charging an EV?

To get an idea of how emissions from charging an EV may change in the coming years, I looked to the Annual Energy Outlook updated most recently in June of this year by the U.S. Energy Information Administration (EIA). The outlook projects changes in the electricity grid expected in the coming years as a result of varying energy demand, regulatory drivers, expected power plant retirements, and other factors.

Using the same well-to-wheels methodology used in our State of Charge report (more on this in the notes below), and the Annual Energy Outlook’s projections for 2025, I estimated how the emissions from charging an EV powered by the grid in 2025 compare to the emissions of a gasoline vehicle. I did this analysis across each of the grid regions across the United States, excluding Hawaii and Alaska for which projections were unavailable.

For each region, I show the miles per gallon that a gasoline vehicle would need to achieve to have emissions similar to an EV powered on the electricity grid (see the map below). For example, charging an EV in Massachusetts on the 2009 regional (NEWE) electricity grid (the most recent year for which we have data) would create about the same global warming emissions as driving a gasoline vehicle that gets 75 mile per gallon. That’s better than any gasoline or hybrid vehicle on the market. In 2025, as the grid in Massachusetts gets cleaner, that same electric vehicle would be responsible for about the same emissions as a gas-powered vehicle with the astounding fuel economy of 106 mpg.

The maps show how EV emissions stack up across the country, with current data and projecting to 2025. Both maps stick with the same GOOD, BETTER, BEST ratings we used in State of Charge, where BEST means an EV has lower emissions than the even the most fuel efficient gasoline hybrid available today (50 mpg). By 2025, four additional regions move into the BEST category and another three move from GOOD to BETTER. A closer look at the map reveals the change in mpg ratings, and shows every regional electricity grid getting cleaner between 2009 and 2025

If the population distribution remains similar, 70 percent of Americans will live in BEST regions by 2025, where a grid powered EV will emit less global warming emissions than a 50 mpg gasoline vehicle. That holds true for about 45 percent of Americans today.

The improvement in emissions is expected as regions around the country clean up their electricity grids. EIA projections show renewables increasing their share of national electricity generation from about 11 percent in 2009 to about 15 percent in 2025. The projections also show the share of our grid powered by coal, the largest source of global warming emissions from electricity production, decreases from 44 percent in 2009 to about 38 percent in 2025.

National numbers don’t tell the whole story

These national figures are positive, but they don’t reflect the magnitude of what’s happening in many regions.

For example, the California grid region is expected to reach 35 percent of its electricity from renewables by 2025, a large change prompted by a strong state Renewable Electricity Standard (RES). As a result, the mpg equivalent of an EV in California is well over 100 mpg by 2025.

In contrast, the Rocky Mountain grid region (RMPA on the map) also sees relatively strong growth in renewable electricity, increasing to about 17 percent of its electricity generation by 2025 from about 10 percent in 2009. But the region remains in the GOOD category as a result of a continued reliance on coal for the vast majority of its electricity needs.

The future has yet to be written

Clean electricity policies are driving the grid in the right direction, meaning an EV bought today is likely to have lower global warming emissions over time.

Some regions are lagging behind, but we have opportunities to change that. In Michigan, currently classified as a GOOD region, a renewable energy standard is likely headed for the ballot this fall. According to a letter from experts across Michigan, the 25% renewable electricity by 2025 standard will not only reduce global warming emissions, but will create jobs, reduce air pollution, and boost the state’s economy.

State and federal renewable energy policies are critical for cleaning up the grid and unleashing the full potential of EVs. The future state of charge looks strong, and with the right policies in place will only get better.

Some notes on the analysis:

I relied on the same methodology from State Of Charge. However, the EPA recently released a new version of their eGrid database with power plant data from 2009. When we released our analysis in April, the most recent data available was from 2007. All our State of Charge materials have been updated with the new info at www.ucsusa.org/EVfacts.

The data source for 2025 is different than 2009 (EIA Annual Energy Outlook (AEO) versus EPA’s eGrid). The AEO provides CO2 power plant combustion emissions data for 2025, but no data on methane (CH4) or N2O emissions which also contribute to global warming. As a result these emissions are not captured in the 2025 estimate. These emissions represent less than 1 percent of total well-to-wheel emissions in each region, based on the 2009 power plant data, so their exclusion in the 2025 estimates is not expected to have a significant impact on the results.

The upstream emissions (those released prior to the combustion of fuel at the power plant) of all three pollutants are, however, captured in both 2009 and 2025 estimates. The upstream emission factors used are the same for 2009 and 2025 (from Argonne’s GREET model).

Alaska and Hawaii are not represented in AEO2012 data, so no 2025 estimates are provided.

The same carbon intensity for a gallon of gasoline is used for 2009 and 2025. Carbon intensity of gasoline is likely to grow given the move towards more unconventional oil sources. If that is the case, the mpg equivalent values for for electric vehicles in 2025 would be too low.

Finally, the comparison uses average emissions intensity for both 2009 and 2025. This is consistent with our methodology in State of Charge and a carbon accounting type methodology, which treats all electricity consumption equivalently.

About the author:
Don Anair is a senior engineer with expertise on diesel, hybrid and battery electric vehicle, and goods movement technologies and the policies needed to turn them into real solutions for U.S. oil dependence, air pollution and global warming. He holds a master’s degree in electrical engineering. See Don's full bio.

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http://www.archwoprk.com Quentin Parker

There are a bunch of “IFs” here, too many to accurately predict your good ‘results’. CA will not reach 35% of renewable grid energy by 2025. Just isn’t realistic. Coal on the US grid will not diminish to 38%, you forget just how powerful THEIR Lobby is. Shale and tar sands will have much greater negative impact as these come on line. They too, will, because of $$$.

Getting power from a national grid vs. a green micro grid system is the main problem here, since incentives for legislature and the executive are driven by the profits of the Lobby in question. We have no true incentive to reduce GHG emits because right now every other EV driving has a huge coal smoke stack spewing GHGs into the air. over 50% of our grid IS coal. think about this, let alone the life cycle costs of EVs, from cradle to grave, including toxicity of our battery packs and THEIR life cycle true costs.

Electrics? BAD IDEA, until mirco fuel cells H2, come along at reasonable prices, and yes, If we collectively decide to travel LESSS. .

Rob Smithers

Never let facts get in the way of a good alarmist reply hey Quentin? Coal on the US grid for the year to date in 2012 has been 35.2%, for 2011 coal supplied 42% and 2010 44% the last year coal supplied over 50% of the grid was 2003 and it has steadily declined since then. I agree that coal on the grid is unlikely to be 38% by 2025, I think it’s far more likely to be ~20%. http://www.eia.gov/electricity/monthly/xls/table_1_01.xlsx

Paul Scott

Quentin, if you are really concerned about the effluent from dirty electricity, why are you running your home on that same dirty power? If you have a good roof for solar, that is already a cheaper solution, all things considered. If you are a typical American living in a single family home, then you are most likely wasting more kWh than you would use to drive an EV. So, just by becoming more efficient you could eliminate 100% of the pollution from your driving by using these otherwise wasted kWh in your car.

http://solarchargeddriving.com Christof Demont-Heinrich

Very interesting analysis and great graphics

Don, I am very interested in contacting you with several questions I have about the environmental impact of EVs “charged” by home solar, both directly, and via solar offset. I’m not going to pose them here because they’re a bit too long for a comments field – hopefully that won’t scare you off

You can track me down at editor(AT)solarchargeddriving.com. I would be delighted to hear from you.

I believe that the actual environmental benefit of BEV in Metropolitan areas is much greater than normally calculated.
A typical trip profile for my weekend consists of less than 10 miles over a 4 hour period with 4 to 6 stops with parking duration’s ranging from 15 min to 2 hours between driving periods of 0.5 to 2.0 miles.
This type of drive-cycle in ambient temperatures of 30 to 50 deg.F with an ICE vehicle would prevent the ICE from ever reaching normal operating temperature and always run with “Cold Enrichment’s”.
When I take my Chevy Volt for the same trip, I will have used about 20% of my battery charge and contributed zero grams of pollutants.

http://opaquemelodies.com David Mooney

Electric cars would certainly be a vast improvement over the internal combustion variety, but they perpetuate the underlying problem of “the car culture.” We need to think much deeper than simply changing the power train on cars.

Wolfgang Uhl

Mobility is an essential part to our quality of life.
The BEV makes it possible to enjoy this freedom without any impact on the environment. (As long as we get our electricity from renewable energy sources)
We need a global initiative and commitment to generate electricity from renewable sources which do not negatively effect our environment.

Jeremy Winick

This is discouraging for someone who lives in Colorado. I gather the projections are based upon estimates of the source of electric power. Many coal fired power plants have been replaced by natural gas even since 2009 with the decreased cost of natural gas (although most of that is probably due to fracking and it has other costs). But since I already use a Camry hybrid that I am getting 42mpg, I am doing better than you project with an electric plugin. Is this true?

http://www.ucsusa.org/news/experts/don-anair.html Don Anair

Based on the average electricity grid mix in rocky mountain grid region (RMPA), it is correct that your Camry hybrid, at 42 mpg, has lower global warming emissions than a typical electric vehicle. But keep in mind there are options for choosing cleaner sources of electricity. A quick look at a list maintained by the Department of Energy shows a number of voluntary programs offered by utilities in Colorado as well as options for buying renewable energy credits. For example, Xcel Energy offers a program to purchase wind power. The wind power that is generated is above and beyond what is required by law, so opting into these programs can help support further renewable energy investments. There are also incentives for residential solar systems if that is an option you want to consider. Pairing an EV with clean electricity is a good choice no matter where you live, even if your region’s electricity grid as a whole is lagging behind.

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